Question details

AI830 in AC800

In setting tab "Signal Range channal 1"="Pt100, -80..80 C", in properties tab I choose Min = -80 and Max = 80. The signal is now configured as -80=-80 and 80=80, and the value shown is 22 C.

Now I know that the value will vary between 20 and 25 degrees. When I look at the bargraph shown in the faceplate, it will be in the range -80 to 80 and a fluctuate in a span 20-25 degrees will barely be visible in the bargraph.

So therefore I change the Min and Max for the signal to Min = 15 and Max = 30. The bargraph in the faceplate have the range of 15 to 30. The "Signal Range channal 1" is still "Pt100, -80..80 C". The measurement will therefore be scaled to 4 C.

I would like to be able to have Min = 15 and Max = 30 but have left readings unchanged ie 22 C. In database (AC450) for AI is there DispMin and DispMax which determines how the bar graph is displayed in the object image and the measured value is not scaled again.

Answers

0

It depends on which library you are using for Analog signal handling. Some libraries might let you configure this while other libraries only use the range configured in the IO channel. I guess your libraries dont have a DISP_MAX or DISP_MIN setting.

You can solve this in a couple of ways ....

If you only want to do this for a single signal (or just a few), then "Override" the Faceplate Element for this signal and change the Bargraph Min and Max Settings for your signal.

If you want to do this for a lot or All of your signals then the simplest way is tomake a new Object Type.

I remember once i have same problem with PT-100. then I tried to give Min and Max Range of the pt-100 not the operational Range. go to properties tab and give Min and Max of Pt-100. then you will have pt-100 scale on faceplate but your reading will be correct.

Assign -80 & 80 in hardware(since its default setting fro pt100) & where as for to display in faceplate you do the following limit the range from 15 to 30 using the limit function block & give that value to faceplate, I did it works fine.